So, the unsafe water, gets treated, margin added and still cheaper as coke than local drinkable water.
Not sure what to say at this.
The main ingredient in Coca-Cola is filtered water. If Coke is cheaper than water in these communities, then why isn't the company selling bottled water for the same price? Their bottling and distribution costs would be the same, while the cost of ingredients would decrease.
It makes no economic sense for Coca-Cola to not sell bottled water in this context. Lacking an economic motive, what's left? Is the assertion that Coca-Cola is actively malevolent and is using their economic power to harm people on purpose at their own expense?
If Coca-Cola is selling bottled water, then another company could come in and start selling bottled water as well, and there's really nothing interesting to differentiate them. But while another company can sell soda, they can't sell Coke. So getting people used to Coke means they'll always instinctively reach for Coke when they're thirsty.
But if something changes the water shortage, either environmental or technological, then Coca-Cola is still in a good position.